A heat-exchanger shell is known having a generally cylindrical outer tube provided internally with an axially and longitudinally extending partition. Such shell types include the two-pass shell with longitudinal baffle, the split-flow shell, and the double split-flow shell, as described on page 11-4 of CHEMICAL ENGINNER'S HANDBOOK, by J. H. PERRY (McGraw-Hill: 1963). The partition wall subdivides the interior of the shell into two separate longitudinally extending compartments that normally communicate at one end at least of the shell. For most efficient heat exchange the partition should form a relatively tight seal along both of its longitudinal edges so that flow between the compartments is only possible in the intended regions, that is at the end or ends of the shell.
Typically such a structure has been formed by using a rectangular partition plate having a width slightly smaller than the internal diameter of the tube forming the outer wall of the shell so that the longitudinal outer edges of this plate are spaced slightly radially inwardly from the inner wall surface of the shell when the plate is positioned on a diametral plane. Seals are provided between the longitudinal edges of the partition plate and the tube forming the outer wall of the shell normally in form of austenitic-alloy seal strips that are bolted or riveted to the longitudinal edges of the partition plate. Each such seal strip has a bent-over edge which lies on the internal face of the tube shell. It is also known to mount a stack or several layers of such L-section seal strips, and to allow limited elastic deformation of them. Nonetheless such arrangements typically leak somewhat, in particular at the holes where the mounting screws or rivets for the seal strips are provided. Furthermore the assembly of such an arrangement with the fitting-together of the partition and tube shell is a relatively complex task that often entails considerable production cost.